1. Field of the Invention
The present invention relates to a tube spacer for arranging heat transfer tubes of a heat exchanger or other tubes at predetermined intervals, a method of manufacturing the tube spacer, and a heat exchanger with the tube spacer.
2. Description of the Related Art
An example of tube spacer is shown in FIG. 14 (Japanese examined utility model No. 25400343). The tube spacer 9A shown in FIG. 14 is formed a meandering shape by bending a wire rod, and has a plurality of straight portions 91 at intervals via clearances 90. A plurality of heat transfer tubes 94 are inserted individually in clearances 90. With this structure, the tube spacer 9A arranges the heat transfer tubes 94 at predetermined intervals. Since the tube spacer 9A is formed from a wire rod, the manufacturing cost is low.
However, the above-described conventional structure has the following problems.
The spacer 9A is bent the wire rod like a mere meander. Therefore, when the heat transfer tubes 94 is secured, the heat transfer tubes 94 should be inserted into clearance 90 in axial direction (the heat transfer tube 94 should be inserted in perpendicular direction to paper surface in FIG. 14). As a result, such insertion is not easy. Although it is convenient that the tube spacer 9A can be inserted from one side of the heat transfer tubes 94, such operation is difficult. Also, the tube spacer 9A is held in contact with the heat transfer tube 94 at merely a point. Therefore, this structure is not stable to support the heat transfer tube 94.
FIG. 15 shows another example of conventional tube spacer (PCT/WO2005/108875). As shown in FIG. 15, the tube spacer 9B has a structure that a plurality of projections 93 is provided on a side of a base plate 92.
According to this spacer 9B, the projections 93 are inserted between desired tubes (not shown) from one side of the tubes, and the clearances of the same to thickness of the projections 93 can be formed between the tubes. The tubes are stably supported because the contact area of the projections 93 and the tubes is large.
However, the cost of the tube spacer 9B is comparatively high because the tube spacer 9B is made of plate material. An example of heat exchanger has a structure that includes a plurality of heat transfer tubes for recovering heat from combustion gas passes through between the heat transfer tubes. When the tube spacer 9B is used for this heat exchanger, the flow of combustion gas is disturbed because the base plate 92 and the projections 93 are wide and combustion gas is interrupted to flow by the base plate 92 and projections 93. Such a phenomenon is not preferable in view of heat exchange efficiency.